Influence of Candelilla Wax on Mechanical Strength, Thermal Stability, and Moisture Resistance of Cassava-based Thermoplastic Starch Composites

Abstract

A bio-based reinforcement strategy was studied as a means to overcome the inherent weaknesses of thermoplastic cassava starch (TPCS), namely its low mechanical strength and high susceptibility to moisture. Candelilla wax, a natural hydrophobic additive, was incorporated into TPCS at different loadings (0, 2.5, 5, 7.5, and 10 wt %) and processed via hot-press compression moulding. The fabricated composites were characterised to examine the effects of wax addition on their mechanical, thermal, and moisture-resistance performance. Mechanical tests (tensile, flexural, and impact), with scanning electron microscopy (SEM), thermogravimetric analysis (TGA). The incorporation of candelilla wax notably improved the material’s performance, particularly at 5 wt%, where tensile strength and modulus increased 77.4% and 615%, respectively. Flexural and impact strength also increased, indicating enhanced toughness. The SEM micrographs showed rougher fracture surfaces with increasing wax, while Fourier transform infrared spectroscopy (FT-IR) confirmed intermolecular hydrogen bonding between starch and wax. Improved thermal stability and reduced water sensitivity were also observed, with the 10 wt % wax composites exhibiting the lowest moisture absorption, solubility, and swelling. Overall, candelilla wax proved effective in strengthening TPCS both structurally and functionally, highlighting its potential for sustainable biodegradable materials in moisture-sensitive applications.